Impression control mechanism



April 20, 1965 Filed Aug. 24, 1961 1-. s. BOLTON 3,179,226

IMPRESSION CONTROL MECHANISM 2 Sheets-Sheet 1 INVENTOR Theodore 5. Bolton ATTORNEYS April 20, 1965 Filed Aug. 24, 1961 'r. s. BOLTON 3,179,226

IMPRES S ION CONTROL MECHANI SM 2 Sheets-Sheet 2 INVTEN 1 OR Theodore S. Bolton United States Patent Ofiice 3,l7,226 Patented Apr. 20, 1965 3,179,226 IWRESSEON CGNTROL IviECHANISlt i Theodore S. Bolton, Fayetteville, N.Y., assiguor to SQM Corporation, a corporation of New York Filed Aug. 24, 1961, Ser. No. 133,665 6 Claims. (til. 197-437) This invention relates to typewriters and the like, and, more particularly, to an improved impression control mechanism for obtaining uniformly dense impressions from type characters of varied printing areas mounted in pairs on type bar members actuated by a power member having a fixed, predetermined power stroke. Specifically, this invention relates to an improved impression control mechanism of the type described above wherein the members of each pair of characters are of different printing area and are alternatively shiftable to a position from which they may be actuated against a print receiving surface.

In order for a typed page to have a pleasing appearance, each of the typed characters thereon should have the same color density, regardless of the size of the character. It is apparent that if all of the type characters strike the print receiving surface with equal force this result will not be obtained since the striking force which would cause a large character to make only a light impression would cause a small character to make a considerably darker impression. To produce uniform impressions, therefore, it is necessary to provide impression control mechanism for individually varying the printing impact momentum and thus the striking force of the various type bars which normally mount type characters having varied printing areas.

conventionally, an upper case and a lower case character are mounted on each type bar. Since, normally, themembers of these pairs of characters each have different surface areas, the impression control mechanism must also be adjustable to compensate for this area difference.

impression control mechanisms of this general description are well known to the prior art. An earlier type of impression control mechanism was employed in conjunction with a pivoted actuator, operatively connected at one end to a type bar and having, at its other end, a

toothed portion adapted to engage cooperating teeth on a power roll. The impression control mechanism comprised an adjustable abutment member arranged to ride the toothed portion ofthe actuator out of engagement with the power roll at a predetermined point and thereby control the momentum imparted to and therefore the striking force of the actuator. For further varying the momentum when the upper case (or in some instances, the lower case) character was shifted into position conditioning it for printing, a torsion spring was so disposed that it would be engaged by an abutment fixed to the type bar during the terminal portion of the type bar stroke; i.e., after the actuator had been disengaged from the power roller. The spring thus reduced the momentum with which the moving type bar was propelled against the print receiving surface. In this type of impression control mechanism, the type bar engaging portion of the torsion spring extended through a slot in a metal tab which could be bent to vary the point of engagement of the spring and the type bar and, therefore, the momentum decreasing effect of the spning.

by United States Patent 2,750,022, issued to Long, June 12, 1956, for Type Bar Impact Control, was employed with a smooth surfaced power roll and a serrate-faced cam, pivotable about the same axis as, and adapted to rotate a type bar actuator. The impression control mechanism for varying the momentum imparted to the actuator comprised a rotatable shaft provided with a plurality of circumferentially spaced rows of independently adjustable stops, one member in each row being adapted to be operatively associated with each of the cams. By rotating the shaft and thereby positioning alternate ones of the stops in the path of travel of the cam, the momentum imparted to the actuator could be independently varied for upper and lowercase characters. Rotation of the shaft was accomplished by depression of a shift lever which, at the same time, shifted alternate members of pairs of characters mounted upon conventional type bars into positions conditioning them for printing. Although this form of impression control mechanism pro duced more uniform impressions than the previously employed devices, it was extremely complex and, therefore, was expensive to manufacture and maintain.

A later, further improved type of impression control mechanism of the class with which this invention is concerned was also employed with a smooth power roll and a serrate-faced cam which imparted momentum to a pivoted type bar actuator. The impression control mechanism comprised a lever mounted on the actuator which was adapted to engage a cam mounted on an elongated, axially shiftable bar at a predetermined point in the power stroke and change the center of rotation and thus the acceleraticn ofthe actuator. By altering the point of engagement of the control lever and the cam, the momentum imparted to the actuator could, of course, be varied. The bar was shifted longitudinally when a shift lever was depressed, bringing a second cam into operative relationship with the control lever, and thus affording a second independent impression control for upper case characters.

In this type of impression control mechanism,-adjustment was a cumbersome, time consuming task since it was necessary, to vary the impressions produced by the characters on a single type bar, to remove both the upper and lower case cams from the bar and replace them in altered position. Typical structure of this type is shown in United States Patent 2,796,966, issued to Toeppen, June 25, 1957, for Type Element Driving Mechanism.

United States Patent 2,907,436, issued to Frechette, October 6, 1959, for Impression Control Device. is typical of the structure resulting from further attempts to produce a simplified impression control mechanism and, at the same time, increase the uniformity of the impressions. To this end, adjustable stops were mounted in pairs on an elongated, pivoted bar, one pair being provided for each type bar actuator (which were of the conventional pivoted type). Depression of a shift lever moved one or the other of each pair of independently adjustable stops into the path of travel of the corresponding type bar actuator. When the actuator engaged the operatively disposed stop, it pivoted the bar against the bias of a spring extending between the bar and a fixed member. By adjusting the appropriate stop, the point of engagement of the actuator and the stop and, therefore, the force absorbed by the spring, could be varied commensurate with the printing surface of the particular character. To produce uniformity of impression with this mechanism, (it is necessary that the biasing spring pivot the elongated bar back to an at rest position between successive engagements by various type bar actuators so that the. succeeding actuator will engage its cooperating stop at the proper point. However, a fast typist can activate the type bar actuators with sufiicient rapidity so that, the bar being pivoted by one actuator, the spring cannot return it to the at rest position before it is engaged by the succeeding actuator. Under such circumstances, uniform impressions cannot be produced.

It is apparent, from the above discussion, that the previously employed impression control mechanisms were defective in at least four respects: (1) they were unnecessarily complicated and expensive to manufacture and maintain; or (2) they were difficult (and, in some instances, impossible) to adjust with the required degree of precision; or (3) evenvwhen properly adjusted, they did not produce satisfactory uniformity of impression or (4) they suffered from a combination of these defects.

Accordingly, the primary objects of this invention include: (1) The provision of an improved impression control mechanism for typewriters and the like which will produce uniform impressions from type bar mounted type characters of varied printing areas;

(2) The provision of an improved impression control mechanism for typewriters and the like which has a minimum number of parts and which is, therefore, easily and inexpensively manufactured, assembled, and maintained;

(3) The provision of an improved impression control mechanism for typewriters and the like which has a plurality of individually and independently adjustable impression controlling members which are readily accessible and which may be quickly and easily adjusted with a high degree of precision to accommodate a plurality of type characters having varied printing areas;

(4) The provision of an improved impression control mechanism for typewriters and the like which will not be affected by the speed with which the operator depresses the keys to activate the type bars to the printing position.

In conjunction with the foregoing objects, it is a further object of this invention to provide an improved impression control mechanism for typewriters or the like in which two independently and individually adjustable impression controlling members are alternately shifted into operative relationship with an actuator for a type bar having a pair of characters of different printing areas mounted thereon when alternate ones of the characters are shifted into the operative position for printing. I

Further novel features and other objects of this invention will become apparent from the following detailed description, discussion and the appended claims taken in conjunction with the accompanying drawings showing a preferred structure and embodiment, in which:

FIGURE 1 is a perspective view of a type bar action employing an impression control mechanism in accordance with the present invention and showing said mechanism positioned for impression control of lower case characters;

FIGURE 2 is a left hand elevational view, partly in section, of the type bar action of FIGURE 1 with the key lever in its normal inoperative position and with the impression control mechanism positioned for impression control of lower case characters; and

FIGURE 3 is identical with FIGURE 2 except that the impression control mechanism is shifted for impression control of upper case characters.

Referring now to the drawings, FIGURE 1 shows a type bar action incorporating an impression controlling mechanism in accordance with the present invention. The type bar action, which is generally similar to that shown in US. Patent 2,798,584, issued to C. H. Kennedy, Ir., July 9, 1957, for Power Actuated Typing Mechanism for Business Machines comprises a key lever pivotally mounted, intermediate its ends, on a shaft 12 which is rigidly attached to a fixedly positioned key lever mounting bar 14. Adjacent the forward end of key lever 10, a compression spring is disposed over a spring guide 22, which extends upwardly from the bottom of an upwardly opening notch 24 formed in key lever 10, with the lower end of spring 20 abutting the bottom surface of the notch. The upper end of spring 20 is disposed over a spring 4 guide 26 which extends downwardly from, and is integral with, a key stem 16 pivotally mounted on key lever 19 by a stud 17. Spring 20 biases an outwardly and downwardly extending hook-shaped stop portion 28 of key stem 16 into engagement with the upper surface of key lever ltl, thus maintaining the key stem 16 in an upright position. A key button 3th is mounted upon the upper end of key stem 16 in any convenient manner.

Pivotally mounted at the rear end of key lever 10 upon a rearwardly extending key lever extension 40 by a stud 42 is a trigger 44. Trigger 44 has a tab 46 whichextends upwardly from forwardly extending arm 47 of trigger 44 and is normally biased into engagement with the lower surface of key lever extension 40 by a spring 48. Spring 48 is connected to and extends between trigger arm 47 and a depending integral tab 52 on key lever 10.

The upper end 54 of trigger 44 (FIGURES 2 and 3) is adapted to engage a horizontal, laterally extending tab 58 on rearwardly and downwardly extending, hook-shaped arm 60 of a cam carrier 62. Cam carrier 62 is pivotally mounted upon a sub-lever 64 by a pivot stud 66. A serrate-faced cam 68 is fixed on an oppositely disposed, forwardly extending arm 70 of cam carrier 62 with its face 72 adapted, upon actuation of lever 10, to transitorily engage the surface of a counter clockwise rotating, motor driven power roll 74.

Sub-lever 64 is pivotally mounted on a shaft 76 which is rigidly attached to a fixedly positioned frame mounted fulcrum bar 78. A spring 80 is attached to and extends between an upwardly and forwardly extending integral limiting tab on sub-lever 64 and forwardly extending cam carrier arm 7 t and biases the forward edge of limiting tab 90 into engagement with the rear face 92 of cam 68 for rotation therewith. A type bar 94 (FIGURE 1) is pivotally mounted intermediate its ends on a shaft 96 rigidly attached to a type bar segment 98. Segment 93 is conventionally mounted for shifting movement between upper and lower case. Type bar 94 is connected to sublever 64 by an elongated, pivotable type bar actuating link 100 fastened between the end of a downwardly extending arm 102 of type bar 94 and an upwardly extending arm 104 of sub-lever 64. Formed on a character holder or type element 106 attached to the end of type bar 94 opposite shaft 96 are upper and lower case type characters 108 and 110.

The impression control mechanism comprises a spring connected to the outer end of a depending integral arm 122 of sub-lever 64 and to the end of one arm 124 of a bell crank 126 pivotally mounted on a shaft 128 disposed in a longitudinally extending slot 121 in a frame mounted bell crank fulcrum bar 130 as is best shown in FIGURES 2 and 3. A second, and weaker, type bar return spring is connected between the end of an oppositely disposed arm 142 of bell crank 126 and an anchor bar 144 attached by screws 146 to fulcrum bar 78 as is also best shown in FIGURES 2 and 3.

Disposed below bell crank 126 is a longitudinally ex tending bell crank stop screw bail which mounts two rows, A and B, of individually and independently vertically adjustable stop screws on a centrally disposed mounting member 162 with a set'screw 164 in row A and a set screw 166 in row B disposed directly below the bell crank arm 142 of each of the type bar actions. Stop screw bail 160- is mounted on, and is adapted to be pivoted about, mounting screws 170 (only one of which is shown) by a lever 172 also jurnalled on mounting screws 170 and pivotally attached to an integral, forwardly extending tab 174 on bail 160 by a stud 176. An oppositely disposed end of lever 172 is pivotally attached to a conventional shift lever mechanism indicated generally at by a stud 182. Shift lever mechanism 180 is connected through an appropriate linkage (which is not shown and may be of any conventional construction) to the usual shift key.

With reference now to FIGURE 2, which shows the tion of the printing stroke.

type action positioned for printing lower case letters, the operation of the above-described mechanism is as follows: Depression ofkey button 3t) rotates key lever 14 (and, therefore, key lever extension 46) clockwise about shaft 12. Clockwise movement of key lever extension 4b first raises the upper end 54 of trigger 44- into contact with tab 58 of cam carrier 60. Then, as key lever extension ll) proceeds to travel clockwise, trigger 44 drives tab 58 of cam carrier so clockwise about pivot stud 66 until cam face '72 engages motor driven power roll '74. The counter-clockwise rotation of power roll 74 drives cam 63 downward at such an angle that the cam face '72 generates a force at pivot stud 66 which rotates sub-lever 64 in a clockwise direction about shaft 76. The clockwise rotation of sub-lever 64 moves type bar actuating link 1% to the right, driving type bar 94 counterclockwise about shaft 96 toward the printing position.

The cam 65% is then driven off power roll 74 ending the power driven portion of the printing stroke.

After the power driven portion of the printing stroke, type bar 94 continues to approach the printing position and, due to the momentum of the moving parts, the pivot stud 66 is increasingly further spaced from the power roll 74- enabling spring 80 to bias cam 68 counterclockwise until its rear face 92 engages limiting tab 99 of sub-lever 64.

Also, after cam 68 has been driven off power roll 74, sub-lever 64 will continue to rotate clockwise about shaft 76 (due to the momentum of type bar 94), thus allowing spring 120 to rotate bell crank 126 counter-clockwise about shaft 123 until bell crank arm 14-2 engages adjustable stop screw 16 1- (indicated as position C in FIGURE 2). After bell crank arm 142 engages stop screw 164- and type bar 94 continues to approach the platen, spring 126 yields, and in so doing absorbs and thereby reduces the momentum of type bar 94 during the terminal por- The point on the power stroke at which lever 12s engages screw 1&4 determines the magnitude of momentum absorbed and thereby the magnitude of the residual impression producing momentum existing on impact with the paper. Earlier engagement with screw 142 will produce a lighter impression.

After printing impact at the point where type bar 94 reaches printing position, springs 120 and 140 contract to restore type bar 94 to its rest position. Spring 140 biases bell crank 126 clockwise which compels spring 12ft, acting as a solid link, once it has completed its contraction, to rotate sub-lever 64 counter-clockwise about shaft 76, driving link 1% to the left (i.e., toward the rear of the machine) and thereby returning type bar 94 to the inoperative position shown in FIGURE 1.

When key 3t) is held depressed until type bar 94 has returned to its inoperative position, the upper end 54 of trigger 4 1 is positioned in front of cam carrier tab fi thereby preventing a repeat printing cycle. Specially designed triggers may be incorporated in the machine to provide desirable repeat characteristics, but these. are not illustrated and form no part of the present invention.

When key 3 1 is released, key lever 1% is biased in a counter-clockwise direction toward its inoperative position by a return spring (not shown). As key lever extension iil rotates counter-clockwise about fixed shaft 12, trigger dd is cammed by the front edge of cam carrier tab 58 (which, in the manner described above, has already been returned to its inoperative position by spring fail) until the upper end 5 1 of trigger d4 bypasses the lower periphery of cam carrier tab 58, allowing spring 48 to bias trigger tab as into engagement with the lower surface of key lever extension 40, thereby positioning upper end '54 of trigger 44 directly below cam carrier tab 58 for the succeeding operation.

FIGURE 3 illustrates the same mechanism as FIG- URE 2 but shifted for printing upper case characters such as 1%. 'When type bar segment 78 is shifted to the upper case position (indicated by the broken line in FIGURE 1), link 18th is pulled upward, shifting lever 172 clockwise about screw 170 until the set screw 166 in row B is positioned below bell crank arm 142. The mechanism then operates in the same manner as it did in the lower case position as described above with the exception that bell crank 126 now rotates about shaft 128 until bell crank arm 142 engages stop screw 166 (indicated as position D in FIGURE 3) rather than stop screw 164.

Since in the lower case position (FIGURE 2) bell crank arm 142 engages stop screw 164 and in the upper case position (FIGURE 3) it engages stop screw 166, it is apparent that selective control of the impressions produced by upper and lower case characters 108 and may be readily efi'ected by adjusting the independently adjustable stop screws 164 and 166.

Although only a single type bar action has been illustrated and described, it is to be understood that, in practice, a typewriter employs a number of similar actions and that this invention is intended to encompass such an arrangement, completely independent impression adjustment being thus provided for each shifted position of each type bar.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

l. A power-driven typewriter comprising a plurality of type carriers, each having a pair of type characters mounted thereon, means for shifting one or the other of said pair of characters on each of said carriers simultaneously into a position conditioning it for printing, power driven actuator means operatively connected to each of said type carriers for selectively propelling the conditioned characters against a printing surface, and means for independently varying the impression producing force of each of the type characters, said last-named means comprising a fixedly positioned pivotally mounted bell crank for each of said type characters, a tension spring connected between each of said actuators and one end of the corresponding bell crank, an elongated shiftable base means substantially horizontally disposed beneath the respective other ends of said bell cranks, two longitudinally extending parallel rows of independently adjustable abutment members extending through said base means, one of the abutment members in one of said rows and one of the abutment members in the other of said rows being located directly beneath the other end of each of said bell cranks, and means operatively associated with said character shifting means for shifting one or the other of said rows of members into operative relation with the said other ends of said bell cranks when said character shifting means is operated to shift one or the other of the members of said pairs of characters into the conditioned position.

2. in a typewriter, a type bar, a power roll, an actuator operatively connected to said type bar and adapted for transistory contact of fixed, predetermined duration to said power roll, to impel the type bar into printing engagement with a platen, means connected to said actuator biasing said type bar toward a normal inoperative position, means for shifting said type bar between alternative positions to selectively condition said type bar to print either lower or upper case characters and a pair of individually and independently adjustable members rigidly positionable in response to character shift movement of said type bar in predetermined fixed position relative to said type bar, said biasing means including a member adapted to abut one or the other of said adjustable members when said type bar actuator is transistorily contacted by said power roll and has caused said type bar to move a predetermined distance to selectively vary printing con tact and the biasing force of said biasing means, said biasing means operating to bias said type bar to its inoperative position only after predetermined movements imparted to said type bar by contact of said actuator to said power roll.

3. The typewriter of claim 2 wherein said biasing means comprises a pair of connected tension springs of differing strengths, and said individually and independently adjustable members are adapted to mechanically isolate said type bar from the etfect of the weaker of said springs after predetermined magnitudes of motion of said type bar from its rest position toward its printing position.

4. A power driven typewriter comprising at least one type bar member, a pair of type characters mounted thereon, means for shifting said type bar member between alternative positions to selectively condition one or the other of said characters for printing, a type bar member actuator, means operably connecting said actuator to said type bar member, a driving member having a predetermined fixed power stroke, means for contacting said actuator in driving relationship with said driving member, and means for selectively varying the momentum of said actuator at the time of printing impact of said type character, said last-named means comprising a single resilient member directly connected to said actuator to absorb part of the momentum imparted to said actuator by said driving member during at least a terminal portion of the stroke of said type bar, a pair of individually and independently adjustable members rigidly positionable in a predetermined fixed position relative to said type bar, said resilient member being connected to a member adapted to abut one or the other of said adjustable members when-said type bar moves a predetermined distance, and means for moving one or the other of said adjustable members into operative association with said resilient member to vary the force exerted by said resilient member when one or the other of said characters is shifted into a position for printing.

5. The power driven typewriter of claim 4, wherein said resilient member is connected to one end of an elongated centrally pivoted member and one or the other of said adjustable members is operativ'ely associated with said resilient member by abutting the oppositely disposed end of said pivoted member when said type bar moves through a predetermined distance.

6. The power driven typewriter of claim 5, wherein said elongated centrally pivoted member comprises a pivotally mounted bell crank, with a tension spring con nected between said actuator and one end of said bell crank, and said pair of rigidly positionable independently adjustable abutment members disposed adjacent the other end of said bell crank in fixed position relative to said type bar.

References tilted by the Examiner UNITED STATES PATENTS 2,798,584 7/57 Kennedy 197l7 2,907,436 10/59 Frechette 197-17 WILLIAM B. PENN, Primary Examiner.

ROBERT A. LEIGHEY, Examiner. 

2. IN A TYPEWRITER, A TYPE BAR, A POWER ROLL, AN ACTUATOR OPERATIVELY CONNECTED TO SAID TYPE BAR AND ADAPTED FOR TRANSISTORY CONTACT OF FIXED, PREDETERMINED DURATION TO SAID POWER ROLL, TO IMPEL THE TYPE BAR INTO PRINTING ENGAGEMENT WITH A PLATEN, MEANS CONNECTED TO SAID ACTUATOR BIASING SAID TYPE BAR TOWARD NORMAL INOPERATIVE POSITION, MEANS FOR SHIFTING SAID TYPE BAR BETWEEN ALTERNATIVE POSITIONS TO SELECTIVELY CONDITION SAID TYPE BAR TO PRINT EITHER LOWER OR UPPER CASE CHARACTERS AND A PAIR OF INDIVIDUALLY AND INDEPENDENTLY ADJUSTABLE MEMBERS RIGIDLY POSITIONABLE IN RESPONSE TO CHARACTER SHIFT MOVEMENT OF SAID TYPE BAR IN PREDETERMINED FIXED POSITION RELATIVE TO SAID TYPE BAR, SAID BIASING MEANS INCLUDING A MEMBER ADAPTED TO ABUT ONE OR THE OTHER OF SAID ADJUSTABLE MEMBERS WHEN SAID TYPE BAR ACTUATOR IS TRANSISTORILY CONTACTED BY SAID POWER ROLL AND HAS CAUSED SAID TYPES BAR TO MOVE A PREDETERMINED DISTANCE TO SELECTIVELY VARY PRINTING CONTACT AND THE BIASING FORCE OF SAID BIASING MEANS, SAID BIASING MEANS OPERATING TO BIAS SAID TYPE BAR TO ITS IN- 